1. Field of Invention
The present invention relates to a retention device, and more particularly to a retention device for locking and fixing a circuit board without bolts.
2. Related Art
Currently, with the rapid development of science, technology and information, a computer device has become a quite popular electronic device. In the current market, computer devices, such as desktop computers, notebook computers, or servers, are all provided with a mainboard therein as a kernel member of a compute system, so that computer peripheral hardware, such as a central processing unit (CPU), a memory module, and a PCI card, electrically connected to the mainboard may perform default functions successfully.
The mainboard is usually fixed as follows. A plurality of conductive bosses is formed on a case of a computer device as fixing means, and a plurality of through holes corresponding to the conductive bosses is formed in the mainboard. The mainboard is laid on the conductive bosses to keep a suitable distance from the case, and then, a plurality of bolts penetrates the through holes of the mainboard, and are locked on the conductive bosses, with a result that the mainboard is suspended by the aid of the conductive bosses, and leg contacts on the back side of the mainboard are prevented from directly contacting the case to cause a short circuit.
With regard to the conventional method of locking and fixing the mainboard by the conductive bosses, when the mainboard is being mounted and dismounted, a user has to lock and release the bolts one by one with the same actions, which is quite complicated and time-consuming and also inconvenient in practical use. Furthermore, the present electronic device is required to be light, thin, short, and small, but too many conductive bosses will occupy more area of the mainboard. The circuit layout on the mainboard cannot be achieved easily, and the volume of the whole electronic device cannot be microminiaturized, either.
In recent years, a thumb screw emerges is developed, which may be screwed directly by hand, so as to serve as a positioning means for fixing the mainboard. As shown in FIG. 1, it is a schematic view of fixing a circuit board 20 on a case 10 using a thumb screw 60 under a normal circumstance. The case 10 has a plurality of positioning posts 11 with a screw hole 61, in which a neck 12 is formed around the middle portion of each positioning post 11. The circuit board 20 has a plurality of positioning holes 21 corresponding to the positioning posts 11. Each of the positioning holes 21 shapes like a calabash and has a wide section 22 and a narrow section 23, and the front end of each positioning post 11 penetrates the wide section 22 of the positioning hole 21. In this manner, the circuit board 20 may slide on the case 10 by the positioning posts 11, so that the narrow section 23 of each of the positioning hole 21 is engaged into each of the neck 12 of the positioning posts 11. Subsequently, the circuit board 20 may be fixed on the case 10 merely by making the thumb screw 60 penetrate the circuit board 20 and screw it into the screw hole 61.
The method of locking the circuit board on the mainboard by using the thumb screw may significantly reduce the quantity of the conductive bosses and solve the problems caused by the method of locking the mainboard by the conductive bosses. However, the method of locking the mainboard by the thumb screw is still a locking method by screwing, and through this method, the process of mounting and dismounting the mainboard is too complicated and time consuming. Furthermore, the cost of the thumb screw is also higher than that of the conventional bolt, thereby causing a high manufacturing cost.
For person skilled in the art, it is an urgently problem that how to truly fix the mounting position of the mainboard in a screwless manner, and enable users to mount and dismount the mainboard rapidly and conveniently.